Three-dimensional non-linear seismic analysis of asymmetric structures on elastic soil

Abstract

An approximate method for non-linear seismic analysis of three-dimensional two-way asymmetric buildings resting on flexible foundations under bi-directional ground motions is presented. To take into account the soil–structure interface effect, the sub-structuring method with frequency-independent soil springs and dashpots was employed. To consider the non-linear behaviour of the structure, a modal stick with five degrees of freedom was used to simulate the multi-degree-of-freedom modal equations for the soil–structure system. Using the bifurcation characteristic of modal pushover curves, the modal stick was modified, by which the coupled modal non-linear translation and rotation deformations were simulated. The seismic responses of two flexibly supported asymmetric buildings (three and eight storeys) were evaluated by the uncoupled modal response history analysis (UMRHA) method employing the proposed modal stick. The seismic responses of the structures were also obtained by employing the rigorous non-linear response history analysis and the results were compared with the corresponding outcomes from UMRHA method. The comparison showed good agreement between the outcomes of the two analysis methods, thus demonstrating that the proposed three-dimensional non-linear analysis technique developed in this study is an effective and applicable tool for dealing with the non-linear analysis of flexibly supported two-way asymmetric-plan structures.